130 NEW ZEALAND MACBO-LEPIDOPTEBA . 



with a thin silken curtain, almost exactly the same shape and size as the numerous 

 marks occurring at intervals on the trunks of many of the trees. Three large tunnels 

 open into this shallow cavity : one in the centre, which runs into the middle of the 

 stem, and one on each side, which run right and left just under the bark. These lateral 

 tunnels are usually very short, but sometimes they extend half-way round the tree, 

 and occasionally even join one another on the opposite side. The central tunnel has 

 a slightly upward direction for a short distance inwards, which effectually prevents 

 it from becoming flooded in wet weather; afterwards it pursues an almost horizontal 

 course until it reaches the centre of the tree, when it appears to suddenly terminate. 

 This, however, is not the case, for, if the gallery floor be carefully examined a short 

 distance before its apparent termination, a round trap-door will lie found, compactly 

 constructed of very hard, smooth silk, and corresponding with the surrounding portion 

 of the tunnel so exactly that it almost escapes detection. When this lid is lifted a 

 Ion-, perpendicular shaft is disclosed, which runs down the middle of the tree to a depth 

 of 14 or 1(> inches, and is about \ inch in diameter. The upper end of this shaft is 

 lined with silk, which forms a framework on which the trap-door rests when closed. 

 The lid itself is of a larger size than the orifice which it covers, and this makes it 

 extremely difficult, if not impossible, to force it open from the exterior, especially as 

 it always fits down very closely as long as the insect remains in its burrow. The 

 object of this contrivance is, no doubt, to prevent the ingress of enemies, large numbers 

 of spiders, slugs, wood-lice, and various orthoptera being frequently found in both 

 central and lateral tunnels, but they are quite unable to pass the trap-door. The 

 galleries of individual larvae are all wonderfully alike, the only differences observable 

 being in the length of the perpendicular shaft, and in the direction of the horizontal 

 burrow, which is sometimes curved. These variations are usually caused by the 

 presence of other tunnels in the tree, which the larva appears to carefully avoid ; at 

 least I have never known an instance where a larva has allowed its tunnel to 

 communicate with another one, whether inhabited or otherwise. 



The caterpillar, when full grown, measures from -11 to 3 inches in length. It is tolerably 

 uniform in thickness, and of a dull yellow colour. The head is large, dark brown, very irregularly 

 striated, and covered with a few short bristles. The first segment is hard and shining with the back 

 and sides ruddy-brown. Its spiracle, which is very large, is situated near the posterior margin, and a 

 little above it there is a dull black spot, tilling a slight concavity about the same size as the spiracle 

 itself. Each remaining segment has on its dorsal surface two horny plates, and two similar plates are 

 situated on inch side immediately below the spiracle. The body of the larva is thinly covered with 

 yellow and black bristles. In many specimens the ventral surface and connecting membrane 

 between the horny plates is pale purple. Younger specimens differ in being of an olive-green 

 colour, which is much more pronounced, when they are small. 



The last act performed by the caterpillar, prior to undergoing its transformation, 

 is the construction of the above-described trap-door at the top of its burrow. This 

 done the insect retreats to the bottom, its posterior segment resting on the termination 

 of the vertical gallery. In^the course of a few days the skin is cast off and worked 

 downwards to the bottom of the burrow, underneath the last segment of the 

 pupa. 



This pupa varies from 2 to 2 J inches in length. It is attenuated in form and pale reddish- 

 yellow in colour. The head and dorsal portion of the thorax are dark brown and hai'der than the 

 rest of the body. The edges of the abdominal segments are furnished dorsally with a row of small 



